Abstract

The reactive power flows affect voltages, losses and transmission capacities. Thus MVAR flows are a matter of increasing concern for the grid operators and the Romanian Regulatory Authority for Energy has established their importance into a specific Order. The latest corresponding regulation for Romania allows the grid operator to exonerate of payment those injections of reactive which affect in a positive manner positively the voltages in the network. Such exemption is difficult to apply since the influence of MVARs on voltages is locational and time dependent. This paper deals with the assessment of reactive powers related to network users for payment and compensation purposes. The drawbacks are evaluated and compared with the benefits for voltage regulation, according to Romanian regulations. Theoretical skills are combined into one organic methodology, and an in-house software package for reactive power assessment is built. This is based on sensitivities of voltage, loss and transmission capacity to reactive injections into nodes. A case study consisting of a real 110kV network of about 2000 nodes was adopted. The survey was conducted for 6000 hours and outlines voltage to sink’s MVARs. The results were used to evaluate the opportunities to compensate and/or to discharge payments the MVARs with positive contribution to voltage regulation. This paper proposes a sensitivity based analysis for a real 110kV network.

Abstract

The paper deals with a preparatory research stage for controlling the air pressure inside a small tank by various characteristics and algorithms. Basic elements both for the hardware design and for the software support are presented. The experimental platform brings together parallel solutions: a microcontroller board using a PICTM 16F877 chip from Microchip and an industrial controller from HoneywellTM. The functionality of the platform will be tested in this stage by the on-line commutation of the control characteristics IN (pressure error) – OUT (PWM control for the air pump). A set for the available characteristics of the controller is stored in software. For a fast design with simulation and debugging capabilities, the author used FlowcodeTM of Matrix Technology Solutions – an Integrated Development Environment with a Very High Level Programming Language. Future research works are intended for some fuzzy control algorithms that could adapt and optimize the control accordingly the dynamic of the process. The main components of the platform are, besides the controllers mentioned above, an industrial pressure sensor, a compressor, the pressurized container and some standard pneumatic devices for a safe operation. Both the hardware and the software design are made so that besides the research aims, the platform could be a flexible and multi – purpose didactic tool for the students.

Abstract

Abstract – This paper presents a model of a Surface Permanent Magnet Synchronous Motor which can be used in a faulty case and a torque ripple control approach developed to be applied if the faulty case is detected. Two faulty cases are considered for study, the first consider an asymmetry between the stator phases of the motor created by unbalanced number of turns and the second a short circuit between the stator windings of the motor. Proposed torque ripple control use a phasor approach to provides the current reference for stator asymmetry and an injection of an inverse current for stator short circuit fault in order to decrease the motor torque ripple. The torque control has been implemented using a model of surface permanent magnet synchronous motor based on the dynamic equations. Simulation and experimental results highlight the link between the faulty and the torque ripple and show the possibility to decrease in this case the torque ripples by changing a balanced sinusoidal current reference by unbalanced one. In practical tests the impact of the unbalanced system of currents in the torque variation is studied using an analysis of vibratory harmonic measured at twice of the supply frequency.

Abstract

It is shown in this paper that the Conservative Power Theory (CPT) describes power properties of electrical circuits in a way which has a strong analogy to this description in terms of Budeanu’s power theory which misinterprets the power phenomena in such circuits. Also, similarly as Budeanu’s power theory, the CPT does not create right fundamentals for the power factor improvement by reactive compensation. Moreover, Budeanu’s power theory is no less “conservative” than the Conservative Power Theory, thus both theories can be referred to as conservative ones.

Content

Professor Aurel CAMPEANU at his 80th anniversary

Professor Grigore CIVIDJIAN at his 80th anniversary

Comparison of the Conservative Power Theory (CPT) with Budeanu’s Power Theory – Leszek S. Czarnecki
Modeling and Torque Ripple Control in Faulty SPMSM – Elmehdi Bahri, Remus Pusca, Raphael Romary, Driss Belkhayat
Digital Control for the Air Pressure with Multi-Characteristics Selection – Dan Mihai
Study of the Reactive Power Side Effects for Tariff and Compensation Purpose at the Transmission Networks’Users – Leonardo Geo Mănescu, Denisa Ruşinaru, Marian Ciontu, Cosmin Buzatu, Eugen Butoarcă, Miron Alba
Evaluating RMS of Linearly Variable Magnitude Waveforms by Using FFT and WPT. Theory and Practice– Ileana-Diana Nicolae, Petre-Marian Nicolae, Diana Cristina Maria, Scărlătescu Lucian
On the Implementation of FBD-Theory Concepts in the Control of Active DC-Traction Substations – Mihaela Popescu, Alexandru Bitoleanu, Mircea Dobriceanu
New Aspects on the Frequency Splitting and Bifurcation Phenomena in Wireless Power Transfer Systems –Mihai Iordache, Andrei Marinescu, Ioana-Gabriela Sîrbu, Lucian Mandache, Dragoş Niculae, Lavinia Iordache
Power Control and Energetic Performances of an Induction Heating System Destined for Drying of Current Transformers – Alexandru Bitoleanu, Mihaela Popescu, Dinu Roxan Doboşeriu
Some Considerations Concerning Radiated Emissions Produced by a Board Display – Petre-Marian Nicolae, Ileana-Diana Nicolae, Relu-Adrian Aipu
Development of a Barrier Structure Actuated by Three Shape Memory Alloy Springs – Sonia Degeratu, Costel Cărămidă, Laurenţiu Alboteanu, Irina Boncea, Daniela Coman, Monica S. Stăicuş, Gabriela Tont
Energetic Analysis of the Drying Process of Cur-rent Transformers from 110 kV Ciungetu Power Station – Dinu Roxan Doboşeriu, Alexandru Bitoleanu, Mihaela Popescu
Improving the Power Quality and Controllability of PV Power Plants for Microgrids Integration – Luminiţa Barote, Corneliu Marinescu, Ioan Şerban, Daniel Munteanu
Simulation and Implementation of Sensorless Control Using Estimators in Electric Drives with HighDynamic – Marcel Nicola, Dumitru Sacerdoţianu, Adrian Hurezeanu
Monitoring and Analysis of the Electrical Parameters for an Industrial Consumer using LabVIEWEnvironment – Claudiu-Ionel Nicola, Viorica Voicu, Sebastian Popescu, Maria Cristina Niţu, Daniela Iovan, Marian Duţă, Alin Benea, Silviu Andreescu
Modeling and Simulation of the Coal Flow Control System for the Longwall Scraper Conveyor – Olimpiu Stoicuţă, Teodor Pană
Design and Simulation of Wireless Power Transfer Systems – Mihai Iordache, George Andronescu, Victor Bucată, Maria-Lavinia Iordache (Bobaru), Marilena Stăculescu, Dragoş Niculae
Small Scale Model of Automatic Barrier Powered by Photovoltaic Panel – Laurenţiu Alboteanu, Gheorghe Manolea, Alexandru Novac
Dynamic Regime Electromagnetic Torque in Brushless Direct Current Motors – Ion Vlad, Sorin Enache, Monica Adela Enache
Enhancing the dynamic frequency of microgrids by means of PV power plants with integrated energy storage – Daniel Munteanu, Ioan Şerban, Corneliu Marinescu, Luminiţa Barote
The Analysis of Magnetic Field Measurements in a Public Access Area – Georgiana Roşu, Octavian Baltag
Comparisons Among p – Channel, n-Channel and Mixed n/p Channel OTFTs – Cristian Ravari, Georgeta Alecu
On the Immunity of Data Acquisition Systems Used in Power Systems – Livia-Andreea Dina, Ileana-DianaNicolae, Petre-Marian Nicolae, Dorina-Mioara Purcaru
Aspects of Behavior Regarding Certain Electronic Equipment Subject to Electrostatic Discharge – Mircea- Emilian Ardeleanu, Paul Nicoleanu
Load Flow Analysis of Unbalanced Distribution Networks using Symmetrical Components Based Software – Denisa Ruşinaru, Leonardo Geo Mănescu, Marian Ciontu, Miron Alba Technical Aspects Regarding Electromagnetic Compatibility Compliance of the Electric and Electronic Integrated Systems – Stoica Dan, Cosereanu Liviu, Enache Mihai, Ploşniţă Albert, Mazăre Petru
Electromagnetic Shielding System for Information and Communication Equipments – Stoica Dan, Cosereanu Liviu, Enache Mihai, Boteanu Adina, Ploşniţă Albert

Annals of the University of Craiova, Series : Electrical Engineering, 2016

Abstract

This paper presents an understandable and friendly Matlab interface, which shows the active filtering role in a simple manner for the users. The created interface allows the active filtering system simulation, choosing the compensation mode. All these are necessary to plot the available workspace variables and to assess the active filtering performance. Moreover it displays the total harmonic distortion values, for the load and grid current, and computes the filtering efficiency The Simulink model was created for a three-phase non-sinusoidal voltage system, the current components being computed using the Conservative Power Theory elaborated by Paolo Tenti. The analyzed system contains a three-phase full wave controlled rectifier with a passive RL load. After the model simulation, the interface will illustrate the grid current and voltage waveforms, before and after the compensation, for both partial and total compensation. The mentioned graphics, as well as the waveform of the reactive current component, will make the user understand the Active Power Filter (APF) functions, i.e. improving the shape of the current absorbed from the power grid and improving the power factor. The created interface can be used as an educational tool in finding that APF is a solution to fix the disturbing effects that non-linear loads, supplied by the power grids, produce to them.

Abstract

This paper contains a review of the scientific literature published till date in the field of power theory for systems with periodic non-sinusoidal waveforms. Dynamic increase in the number of installed nonlinear loads, that are the sources of higher harmonics in current and voltage waveforms, results in deterioration of electrical energy parameters. Higher harmonics lead to corrupted current and voltage waveforms, hence a much worsened energy quality. The number of power theories and papers concerning these issues give evidence about the importance of the problems of working condition optimisation in power systems.

Abstract

This paper presents a method for video information retrieval considering the frames extracted from the video sources through the segmentation of each key frame, the tracking of the salient objects and the domain ontologies. Based on disambiguation algorithms are constructed domain ontologies for annotation of the video contents. An object oriented database is used to store all specific dataextracted by segmenting, tracking, and annotation of the salient objects. The presented technique combines the visual and semantic descriptors with spatial information for a good indexing of data. The object oriented approach used it was imposed by the complex structure of physical objects you can find in the videos as well as the addition of semantic meanings, which must relate to the objects detected. The annotation based on domain ontologies and the pseudonatural query language close to human understanding are a proper contribution of this article, which has led to fulfilling the final goal, the extraction of semantics-based syntax and retrieving the frames with relevant information within a pseudo-natural query language close to human understanding. The results obtained for the sport domain validate the research carried out and represents a model for applying this method on videos from multiple domain of activity.

Abstract

Electronic variable-speed drives can produce large energy and environmental savings in variable-load variable-speed applications when compared with other conventional technologies. There are a very large number of applications which would benefit, both in terms of process improvement and energy savings, through the use of speed control. Previous studies have shown that the variable-flow fluid motion applications (pumps, fans, and compressors) have the largest savings potential. Combined application of inverters and water pumps brings us not only good energysaving benefits but some new problems, such as inverters configuration and overload etc. In systems with high static head the system curve does not follow the curves of constant efficiency. Using the Affinity Laws to calculate energy saving in system with static head is a mistake because it can also lead to major errors. From this element of uncertainty, the thought that we can try a fuzzy approach. This paper presents a theoretical study of use fuzzy logic to control the operation of a variable speed centrifugal pumps. A mathematical model has been realized and a Matlab simulation scheme was attached to it. Based on the mathmatical model of puming systems with or without static head, the article discusses some issues in detail, such as pressure and flow rate regulation. The fuzzy model can be successfully used for the variable speed control of hydraulic systems, whenthe Affinity Lows not observe exactly.

Abstract

The issue of mathematical modeling in order to simulate physical processes or physical systems, permanently preoccupy a significant number of researchers. The sustained efforts being made in this direction are determined by the benefits that simulation can provide and by the development of software packages capable of performing such simulations. It is obvious that mathematical modeling followed by simulation allows the study of possible situations that would be difficult to achieve in real systems and could lead to an irremediable defect. If the mathematical modeling of stationary processes with respect to time is pretty well set, for the transient process simulation is still much to study. The mathematical equations describing such processes are generally of higher order, sometimes they are transcendent, and thus harder to solve. In the paper the authors are concerned with the modeling of transient thermal processes. When analyzing electrical heating systems, the main problem occurs due to heat transfer through the walls. This phenomenon appears at multilayered cylindrical walls, when heat is transferred through it, and a part of it is stored into the wall as internal energy. This paper aims to determine some mathematical relationships which describe the heat storage processes in components with cylindrical geometry. Determined mathematical equations will be used furthermore in the modeling of transient thermal processes in structures with cylindrical geometry. This allows the simulation of multilayer insulation systems under a transient thermal regime for a long time, using Matlab-Simulink toolkit.